Find the displacement in a word problem

AI Thread Summary
A car decelerates at 20 km/h/s from an initial speed of 50 km/h to a final speed of 5.0 m/s. The initial calculations for displacement using the formula vf2 = v02 + 2aΔx initially yielded an incorrect result of 54.4 m. The mistake was identified as a failure to convert units correctly, specifically from km/h/s to km/h/h. After correcting the unit conversion, the accurate displacement is determined to be 15 m.
Natko
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Homework Statement


A car is slowing down at a rate of 20 km/h/s. How far does it travel if its original velocity is 50 km/h and its final velocity is 5.0 m/s?


Homework Equations



vf2 = v02 + 2aΔx

The Attempt at a Solution



vf2 = v02 + 2aΔx
Δx = (vf2 - v02) / 2a
= (182-502) / 2(-20)
= -2176 / -40
= 54.4 m

That's wrong, though. The answer should be 15 m.
 
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Whoops, forgot to convert km/h/s to km/h/h. I got the answer now :)

Natko said:

Homework Statement


A car is slowing down at a rate of 20 km/h/s. How far does it travel if its original velocity is 50 km/h and its final velocity is 5.0 m/s?

Homework Equations



vf2 = v02 + 2aΔx

The Attempt at a Solution



vf2 = v02 + 2aΔx
Δx = (vf2 - v02) / 2a
= (182-502) / 2(-20)
= -2176 / -40
= 54.4 m

That's wrong, though. The answer should be 15 m.
 
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